The need for increased storage capacity and improved read and write access to information stored on magnetic disk drives has produced a large number of improvements in hard disk drive technology. The general trend has been toward increased areal density of information stored on magnetic disk drives, accomplished in part by improvements in the magnetic storage characteristics of materials used to store magnetic information on hard disks and by improved designs and methods of making read and write heads for hard disks. In a thin film write (recording) head, for example, such improvements have resulted in reductions in the width of the pole tips of the write heads in order to increase the track density of the recording medium to which the head writes information. Since higher track densities resulting from narrower pole tip widths allow for more information to be stored on a hard disk, the need to provide further improvements by reducing track width presents a continuing challenge.
Write heads for hard disk drives also desirably benefit from the use of high magnetic fields for writing information on a hard disk. In order for a high magnetic field to be provided by a write head, the magnetic flux density needs to be high in the write head. In turn, higher saturation magnetic moments for write heads are necessary to provide higher flux densities so that areal densities of the magnetic media may thereby also be increased. Materials with high saturation magnetic moments allow for the generation of higher magnetic fields in the magnetic media, increased field gradients, faster effective rise times, narrower pulse widths, smaller erase bands and improved over-write characteristics on the magnetic media. For this reason, it is desirable that the pole tips of a thin film magnetic write head be formed from a high saturation magnetic moment material.
The fabrication of a thin film magnetic head, as well as the various components of the magnetic head, requires that certain submicrometer structures be formed. An example of such a structure is the pole tip of a write head. One method of making pole structures is to fabricate a mask using a photoresist according to a frame plating method in conjunction with a plating process. A typical general sequence for frame plating a pole structure includes depositing a seedlayer on a wafer, spin coating a layer of photoresist on the wafer, imagewise patterning of the photoresist through a mask to expose areas of the photoresist intended to be removed (for a positive-tone resist, or areas intended to be not removed for a negative-tone resist), removal of areas intended to be removed by developing the photoresist to thereby provide a framed opening in the photoresist corresponding to a pole structure, and plating the framed opening to form the pole structure by a conventional plating process.
Resist frame plating methods are also described in the literature. In U.S. Pat. No. 6,547,975 (to Kobrin), for example, a magnetic pole fabrication process is described in which a seedlayer material is sputtered onto the vertical sidewall portion of a polymer layer used to form a submicrometer structure. A “resist frame for plating” method is also referred to in Kobrin based on the disclosure of U.S. Pat. No. 5,665,251.
In U.S. Pat. Nos. 6,635,408 and 6,641,984 and U.S. Patent Application Publication No. 2001/0035343 (all to Kamijima) and U.S. Pat. No. 6,358,674 (to Kamijima et al.), frame plating methods are also described using a resist that may be a chemically amplified resist. The resist is described as being coated with a covering layer of a water-soluble crosslinking agent capable of being crosslinked in the presence of acid and a resin material containing at least a water-soluble resin on the water-soluble crosslinking agent. The covering layer, rather than the resist, appears to be described as functioning as the frame in contact with the plating solution.
As is known in the art, chemically amplified resists (CARS) may be categorized as positive-tone or negative-tone resists. Positive-tone resists generally contain two major components: an aqueous base soluble polymer resin and a photoacid generator (PAG). The aqueous base soluble polymer of such chemically amplified resists typically contains polar functional groups protected by acid-cleavable protecting groups (also known in the art as acid labile, or blocking groups). The presence of such protecting groups converts the aqueous base soluble polymer into an insoluble resin. Acid catalyzed deprotection of the protected sites converts the polymer back into an aqueous base soluble polymer. Development of the positive-tone resist selectively removes the exposed regions of the photoresist.
The acid-cleavable groups used with the aqueous base soluble polymer resins can be classified into two distinct groups: a) high activation energy protecting groups such as t-butyl ester or t-butyl carbonyl groups; and b) low activation energy protecting groups such as acetal, ketal or silylether groups. Hybrid resists are also described in the art in which a combination of high and low activation energy groups is included in the resist (see, e.g., U.S. Pat. No. 6,303,263 to Chen et al.).
Although a wide variety of photoresists are known in the art, the requirements of a specific application may govern the suitability of using a particular resist in that application. For example, in contacting a resist frame with certain plating process solutions, defects such as cracks and “worms” (i.e., localized fractures or irregular defects in the resist) may be introduced into the resist depending on the type of resist, the plating solution and/or the plating conditions used. Such defects, in turn, may lead to irregularities and defects in the plated structures obtained from the plating process.
Thus it is desirable to have a method for making plated components for hard disk drive magnetic heads, particularly the write head poles of a magnetic head, which are essentially free of plating defects. It is further desirable for such a method to provide a means for reducing or eliminating such defects through compatible modifications to existing methods for making plated components for magnetic heads.
Accordingly, the present invention addresses such needs in part by providing an improved method of forming a component of a magnetic head, that, in one embodiment, is suitable for making a plated magnetic component of a write head for use in a hard disk drive.